1. Field of the Invention
This invention relates to a magnetic tape winding device which is used in the case where a predetermined length of a magnetic tape is wound on a small tape reel from magnetic tape roll stock, or in the case where the magnetic tape wound on a tape reel is rewound on another tape reel, or in the case where a magnetic tape is wound to form a magnetic tape roll stock, or in the case where a magnetic tape roll stock wider than a magnetic tape product is cut into a plurality of magnetic tape roll stocks different in tape width, and the magnetic tapes of the roll stocks thus obtained are wound on the tape reels.
2. Background of the Invention
The manufacture of magnetic tapes such as audio cassette tapes, video cassette tapes, memory tapes and broadcasting video tapes include intermediate manufacturing steps such as a step of winding a predetermined length of a magnetic tape onto a tape winding structure such as a tape reel or hub from a magnetic tape roll stock, a step in which a magnetic tape wound on a tape winding structure is rewound on another tape winding structure, a step of winding a magnetic tape to form a magnetic tape roll stock, and a step in which a magnetic tape roll stock wider than a magnetic tape product is cut into a plurality of magnetic tape roll stocks different in tape width, and the magnetic tapes of the roll stocks thus obtained are wound on the tape winding structures.
When the magnetic tape is wound on the tape winding structure in the tape winding step or in the tape rewinding step, depending on the properties of the magnetic tape roll stock on the tape delivery side, or the properties of the tape winding structure on the tape winding side, or the properties of the magnetic tape itself, the magnetic tape is vibrated in the direction of its thickness or width. That is, the so-called "tape behavior" varies, as a result of which the magnetic tape wound on the tape winding structure has an unsatisfactory appearance. That is, the winding surface (formed by the tape edges) of the magnetic tape wound on the tape winding structure is uneven as viewed in the axial direction of the tape winding structure. This tendency is significant when the tape winding speed is high.
If the magnetic tape thus unneatly wound is placed, for instance, in a magnetic tape cassette case, the resultant magnetic tape cassette is low both in appearance and in quality. Furthermore, the magnetic tape is liable to curl or its edge is liable to be damaged, with the results that various troubles are induced or the electro-magnetic conversion characteristic is lowered. The above-described difficulty that a magnetic tape is unneatly wound is a serious problem, for instance, for video magnetic tape for high density recording operation, because audio signals and synchronizing signals rerecorded along the tape edge.
Therefore, in a conventional magnetic tape manufacturing operation, after the above-described magnetic tape winding or rewinding step, the external appearance of each roll of magnetic tape is, for instance, visually inspected to determine whether or not, in each of the magnetic tape rolls, the tape has been neatly wound on the tape winding structure. The time and cost required for the visual inspection greatly lower the efficiency of manufacturing the magnetic tape efficiency.
In the operation of winding a magnetic tape which is liable to be unneatly wound, in order to reduce the burden of the visual inspection or to improve the external appearance of the magnetic tape roll, a so-called "dress winding method" as shown in FIG. 1 or 2 has been employed in the art.
FIGS. 1 and 2 are perspective views outlining the arrangement of a tape winding structure 2 and its relevant components on the tape winding side. In the case of FIG. 1 a flexible endless belt 11 of rubber or polymide rotatably is held by rollers 12, 13 and 14. The flexible belt 11 is turned together with a magnetic tape T while elastically strongly pushing the tape's magnetic surface radially inwardly of the tape winding structure 2 so that the magnetic tape T is neatly wound on the tape winding structure. In the case of FIG. 2, a belt 15 of relatively soft unwoven cloth is provided between one of the flanges of a tape winding structure 2 and the winding surface (formed by the tape edges) of a magnetic tape T. The belt 15 is first wound on the belt forwarding side. While the belt 15 thus wound is supported by rollers 17 and is being rewound on the belt winding side 18 at a predetermined low speed, the magnetic tape T is thereby pushed axially inwardly of the tape winding structure 2 so that the magnetic tape is neatly wound on the tape winding structure 2.
In each of the methods shown in FIGS. 1 and 2, the belt 11 and 15 directly touches the magnetic tape T. Therefore, the methods suffer from difficulties that the magnetic layer is scraped or fibers come off the unwoven cloth, thus resulting in the occurrence of dropouts, or the magnetic tape is pushed so greatly that the tape edge or the tape itself is damaged. That is, the methods cannot be employed as the case may be. Furthermore, the above-decribed dress winding mechanism greatly consumes itself, thus providing another difficulty that the maintenance cost is increased. In addition, the dress winding mechanism is disadvantageous in the following points. The magnetic tape winding device must be so designed that, in replacing the tape winding structure 2, the dress winding mechanism can be moved from the operating position to the standby position and vice versa. That is, the device becomes correspondingly intricate in construction. Furthermore, in such a magnetic tape winding device, the replacement of the tape winding structure takes a relatively long time, and the time required for the movement of the dress winding mechanism obstructs improvement of the productivity.
Two cassette tape winding systems have been employed in the art. One of the two systems is a so-called "open winding system" in which a magnetic tape wound by the aforementioned dress winding method is inserted in a cassette case, to form a magnetic tape cassette. The other is a so-called "in-cassette winding system, or C-O winding system, or V-O winding system" in which a magnetic tape is wound in the final step of the cassette assembling work.
The latter system will be described with reference to FIGS. 3 and 4. All components except for a magnetic tape are built in a cassette case 8. More specifically, a tape winding structure on the tape delivery side and another tape winding structure on the tape winding side are connected through a leader tape 10 to each other. The so connected tape winding structures are inserted into the cassette case 8, and the cassette case 8 is tightened with screws, thus providing a semi-finished product of a magnetic tape cassette (generally referred to as "V-O" or "C-O"). With a tape winding device called "in-cassette winder", the leader tape 10 is pulled out of the semifinished product and cut into two parts. The end of one of the leader tapes is spliced to the end of the magnetic tape to be wound. The other leader is kept held with a holding member 10a which, for instance, sucks and retains a magnetic tape. The tape winding structure 2 connected to the leader tape of which the magnetic tape T has been fastened is turned until a predetermined length of the magnetic tape is wound on it and the magnetic tape is then cut. The end of the magnetic tape thus cut is spliced to the end of the other leader tape fastened to the other tape winding structure 3. Thus, the magnetic tape cassette has been manufactured. In this in-cassette winding system, unlike the above-described method, it is impossible to mechanically touch the magnetic tape at a part of the tape winding structure. Accordingly whether or not the magnetic tape wound is acceptable in external appearance depends on the properties of the magnetic tape and the accuracy of the cassette components. That is, it is completely impossible to control the winding operation to thereby precisely wind the magnetic tape on the tape winding structure. In order to precisely wind the magnetic tape on the tape winding structure, a method has been employed in which, as shown in FIG. 4, a roller 50 having flanges 51 at both ends is arranged at the inlet of the cassette so that a force is exerted on the magnetic tape which is being wound in its widthwise direction. That is, the magnetic tape is pushed towards its one flange. If, in this method, a strong force is applied to the magnetic tape, it may damage the tape edge. On the other hand, application of a weak force thereto cannot make the magnetic tape acceptable in appearance when wound. That is, the method still has a problem to be solved.
Recently, a magnetic tape winding device as shown in FIG. 5 has been proposed in the art (cf. Japanese Patent Application (OPI) No. 51642/1986 (the term "OPI" as used herein means "an unexamined published application"). In the device, a winding drive shaft 30 is detachably engaged with the winding hub 41 of a winding reel 40 which is made up of the winding hub 41 and a single flange 42. At least one magnet 31 is mounted on the winding drive shaft 30 in such a manner that the magnet is located on one side of the flange 42 which is opposite to the other side where a magnetic tape T is wound, so that the magnetic tape T is wound on the winding reel 40.
However, the magnet 31 disposed around the shaft 30 as shown in FIG. 5 provides the following problems. In a magnetic tape roll wound on the winding reel 40, its central portion close to the winding core 41 is lower in neatness than its peripheral portion. This difficulty is based on the following reason. The configuration of the magnet 31 depends on that of the drive shaft 30. That is, the magnet 31 is, for instance, in the form of a ring (having a central hole) so that it can be mounted on the shaft. Therefore, the lines of magnetic force are not regular in direction near the center of the winding reel 40, and the magnetic flux density is smaller. Accordingly, the force attracting the magnetic tape towards the flange 42 of the winding reel 40 is unstable and weak during the initial period of the magnetic tape winding operation.
Since the magnet 31 is placed below the flange, its installation space is limited. Furthermore, the magnet 31 is limited in diameter and configuration by a drive system such as the winding drive shaft. Accordingly, the manufacture of the magnet is rather difficult. That is, the magnet is high in manufacturing cost, with the result that the maintenance cost of the device is high.